Increasing concern, about the health risk due to solid aerosols from engine combustion, has provoked more stringent imission limits, for soot particles in the range of pulmonary intrusion, at critical work-places (e.g. tunnel sites, see Table 1). Within the scope of the joint European project VERT, these emissions were characterized and their effective curtailment through exhaust gas after-treatment investigated. Diesel engines, irrespective of design and operating point, emit solid particulates in the range of 100 nm, at concentrations above 10 million particulates per cm3. Engine tests showed that a drastic curtailment of pulmonary intruding particulates seems not feasible by further development of the engine combustion, nor by reformulation of fuels, nor by deployment of oxidation catalytic converters. Particulate traps, however, can curtail the total solid particulate count, in the fine particulate range 15-500 nm, by more than two orders of magnitude. The effect can be reinforced through fuel additives, such as those promoting regeneration in particulate traps. A field test during 18 months (2000h) proved that several particulate trap systems meet this requirement. Thus the technical feasibility is basically established - the deployment of such particulate trap systems can therefore be demanded under critical exposures. Germany has already mandated the deployment of particulate traps in closed or partly closed working areas.For the study of pulmonary intruding particulates from Diesel engines and the evaluation of the particulate traps systems, the usual gravimetric evaluation of the total particulate mass PM must be abandoned or at least enhanced. This is necessary as gravimetry is non-specific with respect to the chemical composition and the aerosol properties (such as size and surface) and, hence, delivers no toxically relevant information. The counted particulate concentration appears to be the significantly more specific and sensitive criterion. Industrially suitable and field deployable procedures should now be developed based on the dependable laboratory methods.